Monterey Bay Aquarium Research Institute
Marine Botany

Morphology of Articulated Coralline Algae

       Articulated corallines are structurally organized into cellular filaments. Thalli and developed stalks can be either uniaxial or multiaxial, depending on which genera one is taking into account. Algal size and thickness are usually determined by both genetic and environmental factors. 

       The articulates are often referred to as geniculates due to their possession of flexible, uncalcified genicula, which operate like joints. Genicula are the primary characteristic that distinguish the articulates from crustose forms of corraline. Organization of genicula differs between classes of corallines in the numbers of cell tiers or layers. However, the basic structure of these tissues is consistent throughout all articulates. 

pit connection in Bossiella

A genicula from a Bossiella specimen.

        The other primary tissues  in the articulates are referred to as intergenicula. These calcified branch segments are extremely rigid, like bones. Most intergenicula have cuticles that cover their calcium carbonate walls. Intergenicula play a crucial role in the reproduction and growth of geniculates. Reproductive conceptacles develop only on intergenicula. The growth of articulates is dependent upon the elongation of intergenicula and division of these growing segments via the formation of new genicula. Decalcification of the intergenicula reveals underlying tissue just like that found on other red algae.

Calliarthron closeup

Calliarthron and its broad intergenicula.   

       Most articulates have both primary and secondary pit connections between their cells that arise with growth-related cell division. These connections are sealed by the formation of mucosal pit plugs. Another type of interesting cell connection exists within the geniculates--cell fusion. Many coralline cells are able to fuse with other coralline cells from the same or a different plant if cells touch for a prolonged period of time.    

Evolution  |  Ecology  |  Systematics  |  Mechanics  |  Pigmentation  |  Morphology  |  Reproduction  |  Life HistoryReferences  |  Procedures  Acknowledgements  |  Main   

© 2001 Ian Ehrenreich. All rights reserved.